Dough mixers for producing dough used in preparing foods are known which utilize the function of one or two screw conveyors, of rotating mixing arms within fixed or rotating containers with vertical or angled axis, or of kneading elements rotating within a closed housing with a horizontal axis.
The specific level of technology is based on this last type of dough mixer, which thus uses the function of mixing elements rotating within a closed casing on a horizontal axis.                The U.S. Pat. No. 5,486,049 (apparati for mixing liquid substances) refers to a device for mixing liquid substances of varying degrees of viscosity. The stirring element of this device comprises a plurality of rungs that are arranged between two coaxial disks equidistant from each other and to their rotational axis.        The U.S. Pat. No. 4,630,930 (high-speed batch mixer) publishes a method and device for producing a portion of dough. The device comprises two coaxial chambers within which there are separate work phases performed by separate and different mixing or kneading elements. The ingredients for preparing the dough are introduced from above into the first chamber, where they are thoroughly mixed and then transported into the second chamber. In the second chamber they are kneaded by a kneading element that comprises parallel rungs, which are attached at both ends to corresponding radial arms that extend at the same angles and rotate about a common axis. The technical features of the second device requires a previous thorough mixing in a mixing chamber that is separated from the kneading chamber; the casing line of the inside casing surface of the mixing chamber and of the kneading chamber have a rotational axis that is coaxial with the rotational axis of the kneading element.        The U.S. Pat. No. 5,322,388 (dough mixer) publishes a device for preparing dough which comprises a cylindrical chamber with a horizontal axis having in its upper region an opening for charging by free fall the ingredients that are used for preparing the dough, and in its lower region a closeable opening for discharging the prepared dough. The operation within the chamber takes place in the chamber's lower region by using several equidistant agitator blades on the same drive shaft with a rotational axis that is displaced but parallel to the chamber axis. The kneading chamber of this device can be opened because the disk-shaped vertical wall together with the agitator blades and the wall of the casing surface can be moved axially to the second vertical, disk-shaped wall, on which a scraper is located together with the corresponding drive motor.        There are other smaller mechanical devices for preparing dough in the household; generally, they comprise a cylindrical container with a vertical axis within which one or more agitator blades operate on a single drive shaft that is attached coaxially to the container axis.        
All of these known devices are not designed for preparing individual dough portions per each work cycle within relatively short periods of time and by charging with ingredients in individual portions; further, they do not provide that every individual mixed dough portion that is rolled into a ball and is ready for shaping and baking can be discharged without leaving ingredients or dough residue inside the device. The known devices are also not designed to perform a periodic, completely automatic sterilization of the kneading chamber and its kneading elements.
The problem is also known that the charging of the kneading devices with relative exact volumetric metering of the flour or flour-like or dust-like ingredients, which are more or less hydroscopic. Such problems are based on the tendency that flour-like material forms accumulations or agglomerates inside the container, that varying the material volume above the metering mechanism strongly affects the metering process and that it is difficult to achieve an even filling and/or emptying of the metering chamber.